M-139 (Michigan highway)

M-139
M-139 highlighted in red
Route information
Maintained by MDOT
Length:	26.487 mi (42.627 km)
Existed:	September 22, 1929 – present
Major junctions
South end:	US 12 near Niles
	I-94 near Benton Harbor
North end:	BL I-94 in Benton Harbor
Location
Counties:	Berrien
Highway system
Michigan State Trunkline Highway System Interstate US State Byways ← M-138 M-140 →

M-139 is a state trunkline highway entirely within Berrien County in the US state of Michigan. The highway starts at US Highway 12 (US 12) southwest of Niles and runs through rural areas of the county to terminate at an intersection with Business Loop Interstate 94 (BL I-94) in Benton Harbor. The highway runs parallel to the St. Joseph River, crossing the river several times as it follows a set of roads previously used for US 31 in the area. The highway was first designated in the 1930s as a bypass of the Benton Harbor and St. Joseph area. Its termini have been moved over the years since, extending and contracting the length of the highway between Niles and Benton Harbor. M-139 now serves to provide access through the area from a set of bypasses consisting of I-94 and US 31.

M-139 begins at a junction with US 12 southwest of Niles in Bertrand Township. The highway travels northeasterly along Chicago Road through farm fields and residential neighborhoods. The trunkline turns north along Lincoln Avenue and then east on Main Street to run into downtown Niles. Main Street crosses the St. Joseph River, and at the intersection with Front Street, M-139 turns north along that street which is also called "OLD US 31" on some maps. The highway runs parallel to the river as both exit the downtown area. M-139 turns toward the northwest on the outskirts of town, running through farm fields. The trunkline passes Webster and Long lakes as it crosses mixed forest and residential areas between Niles and Berrien Springs.